【IVI】车载设备硬件抽象层VHAL

android12-release
Android Automotive OS知识体系
Android 知识体系

1、概要

车载硬件抽象层 (HAL) 接口会定义原始设备制造商 (OEM) 可以实现的属性，并会包含属性元数据（例如，属性是否为 int 以及允许使用哪些更改模式）。VHAL 接口以对属性（特定功能的抽象表示）的访问（读取、写入、订阅）为基础。

2、HAL 接口

【IVI】VehicleService启动

2.1 VHAL 使用以下接口

hardware/interfaces/automotive/vehicle/2.0/IVehicle.hal

getAllPropConfigs() 会生成 (vecpropConfigs)
列出 VHAL 所支持的所有属性的配置。CarService 仅使用支持的属性。
getPropConfigs(vec<int32_t> props) 会生成 (StatusCode status,vec propConfigs);
返回所选属性的配置。
set(VehiclePropValue propValue) 会生成 (StatusCodestatus);
向属性写入一个值。写入的结果是按属性进行定义的。
subscribe(IVehicleCallback callback, vec options) 会生成 (StatusCode status);
开始监视属性值的变化。对于区域属性，unsubscribe(IVehicleCallback callback, int32_t propId) 会生成 (StatusCode status);

2.2 VHAL 使用以下回调接口

hardware/interfaces/automotive/vehicle/2.0/IVehicleCallback.hal

oneway onPropertyEvent(vecpropValues);
通知车辆属性值的变化。应只针对已订阅属性执行。
oneway onPropertySetError(StatusCode errorCode,int32_t propId,int32_tareaId);
返回全局 VHAL 级错误或每个属性的错误。全局错误会导致 HAL 重新启动，这可能会导致包括应用在内的其他组件重新启动。

2.3 Set 调用

set 调用属于异步操作，涉及所请求更改发生之后的事件通知。在通常的操作中，set 调用会导致在车辆网络中发出更改请求。某些 set 调用可能要求准备好初始数据，而这些数据在初始化期间可能尚不可用。在这种情况下，set 调用应返回 -EAGAIN。某些具有独立的电源开/关的属性应在属性关闭且无法设置时返回 -ESHUTDOWN。在 set 生效之前，get 不一定会返回所设置的值。例如：set HVAC Temperature。

（CS = CarService、VHAL = 车载 HAL）

2.4 Get 调用

在初始化期间，由于尚未收到匹配的车辆网络消息，属性的值可能不可用。在这种情况下，get 调用应返回 -EAGAIN。一些属性（例如 HVAC）具有独立的电源开/关属性。对此类属性调用 get（关闭电源时）应返回 UNAVAILABLE 状态，而不是返回错误。例如，get HVAC 温度

（CS = CarService、VHAL = 车载 HAL）

3、车辆属性

3.1 车辆属性

hardware/interfaces/automotive/vehicle/2.0/types.hal
属性可以为只读、只写（用于将信息传递到 VHAL 一级），也可以为读写（对大多数属性而言对读写的支持是可选的）。每个属性都由一个 int32 键唯一标识，且具有一个预定义的类型 (value_type)：

BYTES
BOOLEAN
EPOCH_TIME
FLOAT
FLOAT[]
INT32
INT32[]
INT64
INT64[]
STRING
MIXED

区域属性可能具有多个值，具体取决于属性所支持的区域数量。

/*** Enumerates supported data type for VehicleProperty.** Used to create property ID in VehicleProperty enum.*/
enum VehiclePropertyType : int32_t {STRING          = 0x00100000,BOOLEAN         = 0x00200000,INT32           = 0x00400000,INT32_VEC       = 0x00410000,INT64           = 0x00500000,INT64_VEC       = 0x00510000,FLOAT           = 0x00600000,FLOAT_VEC       = 0x00610000,BYTES           = 0x00700000,/*** Any combination of scalar or vector types. The exact format must be* provided in the description of the property.** For vendor MIXED type properties, configArray needs to be formatted in this* structure.* configArray[0], 1 indicates the property has a String value* configArray[1], 1 indicates the property has a Boolean value .* configArray[2], 1 indicates the property has an Integer value.* configArray[3], the number indicates the size of Integer[] in the property.* configArray[4], 1 indicates the property has a Long value.* configArray[5], the number indicates the size of Long[] in the property.* configArray[6], 1 indicates the property has a Float value.* configArray[7], the number indicates the size of Float[] in the property.* configArray[8], the number indicates the size of byte[] in the property.* For example:* {@code configArray = {1, 1, 1, 3, 0, 0, 0, 0, 0}} indicates the property has* a String value, a Boolean value, an Integer value and an array with 3 integers.*/MIXED           = 0x00e00000,MASK            = 0x00ff0000
};

3.2 区域类型

区域类型	说明
GLOBAL	此属性是一个单例，不具备多个区域。
WINDOW	基于车窗的区域，使用 VehicleAreaWindow 枚举。
MIRROR	基于车镜的区域，使用 VehicleAreaMirror 枚举。
SEAT	基于座椅的区域，使用 VehicleAreaSeat 枚举。
DOOR	基于车门的区域，使用 VehicleAreaDoor 枚举。
WHEEL	基于车轮的区域，使用 VehicleAreaWheel 枚举。

enum VehicleArea : int32_t {GLOBAL      = 0x01000000,/** WINDOW maps to enum VehicleAreaWindow */WINDOW      = 0x03000000,/** MIRROR maps to enum VehicleAreaMirror */MIRROR      = 0x04000000,/** SEAT maps to enum VehicleAreaSeat */SEAT        = 0x05000000,/** DOOR maps to enum VehicleAreaDoor */DOOR        = 0x06000000,/** WHEEL maps to enum VehicleAreaWheel */WHEEL       = 0x07000000,MASK        = 0x0f000000,
};

3.2.1 WINDOW区域类型 VehicleAreaWindow

/*** Various windshields/windows in the car.*/
enum VehicleAreaWindow : int32_t {FRONT_WINDSHIELD  = 0x00000001,REAR_WINDSHIELD   = 0x00000002,ROW_1_LEFT        = 0x00000010,ROW_1_RIGHT       = 0x00000040,ROW_2_LEFT        = 0x00000100,ROW_2_RIGHT       = 0x00000400,ROW_3_LEFT        = 0x00001000,ROW_3_RIGHT       = 0x00004000,ROOF_TOP_1        = 0x00010000,ROOF_TOP_2        = 0x00020000,};

3.2.2 MIRROR区域类型 VehicleAreaMirror

enum VehicleAreaMirror : int32_t {DRIVER_LEFT = 0x00000001,DRIVER_RIGHT = 0x00000002,DRIVER_CENTER = 0x00000004,
};

3.2.3 SEAT区域类型 VehicleAreaSeat

/*** Various Seats in the car.*/
enum VehicleAreaSeat : int32_t {ROW_1_LEFT   = 0x0001,ROW_1_CENTER = 0x0002,ROW_1_RIGHT  = 0x0004,ROW_2_LEFT   = 0x0010,ROW_2_CENTER = 0x0020,ROW_2_RIGHT  = 0x0040,ROW_3_LEFT   = 0x0100,ROW_3_CENTER = 0x0200,ROW_3_RIGHT  = 0x0400
};

3.2.4 DOOR区域类型 VehicleAreaDoor

enum VehicleAreaDoor : int32_t {ROW_1_LEFT = 0x00000001,ROW_1_RIGHT = 0x00000004,ROW_2_LEFT = 0x00000010,ROW_2_RIGHT = 0x00000040,ROW_3_LEFT = 0x00000100,ROW_3_RIGHT = 0x00000400,HOOD = 0x10000000,REAR = 0x20000000,
};

3.2.5 WHEEL区域类型 VehicleAreaWheel

enum VehicleAreaWheel : int32_t {UNKNOWN = 0x0,LEFT_FRONT = 0x1,RIGHT_FRONT = 0x2,LEFT_REAR = 0x4,RIGHT_REAR = 0x8,
};

3.3 属性状态

每个属性值都有一个 VehiclePropertyStatus 值。该值指示相应属性的当前状态：

项目	说明
AVAILABLE	属性可用，且值有效。
UNAVAILABLE	属性值目前不可用。用于某个受支持属性的被暂时停用的功能。
ERROR	该属性有问题。

/*** Property status is a dynamic value that may change based on the vehicle state.*/
enum VehiclePropertyStatus : int32_t {/** Property is available and behaving normally */AVAILABLE   = 0x00,/*** A property in this state is not available for reading and writing.  This* is a transient state that depends on the availability of the underlying* implementation (e.g. hardware or driver). It MUST NOT be used to* represent features that this vehicle is always incapable of.  A get() of* a property in this state MAY return an undefined value, but MUST* correctly describe its status as UNAVAILABLE A set() of a property in* this state MAY return NOT_AVAILABLE. The HAL implementation MUST ignore* the value of the status field when writing a property value coming from* Android.*/UNAVAILABLE = 0x01,/** There is an error with this property. */ERROR       = 0x02,
};

2.4 配置属性

使用 VehiclePropConfig 为每个属性提供配置信息。具体信息包括：

变量	说明
access	r、w、rw
changeMode	表示监视属性的方式：变化时监视或持续监视。
areaConfigs	areaId、min 和 max 值。
configArray	额外配置参数。
configString	以字符串形式传递的额外信息。
minSampleRate	maxSampleRate
prop	属性 ID，整数

struct VehiclePropConfig {/** Property identifier */int32_t prop;/*** Defines if the property is read or write or both.*/VehiclePropertyAccess access;/*** Defines the change mode of the property.*/VehiclePropertyChangeMode changeMode;/*** Contains per-area configuration.*/vec<VehicleAreaConfig> areaConfigs;/** Contains additional configuration parameters */vec<int32_t> configArray;/*** Some properties may require additional information passed over this* string. Most properties do not need to set this.*/string configString;/*** Min sample rate in Hz.* Must be defined for VehiclePropertyChangeMode::CONTINUOUS*/float minSampleRate;/*** Must be defined for VehiclePropertyChangeMode::CONTINUOUS* Max sample rate in Hz.*/float maxSampleRate;
};

2.4.1 property可读、可写或读写

/*** Property config defines the capabilities of it. User of the API* must first get the property config to understand the output from get()* commands and also to ensure that set() or events commands are in sync with* the expected output.*/
enum VehiclePropertyAccess : int32_t {NONE = 0x00,READ = 0x01,WRITE = 0x02,READ_WRITE = 0x03,
};

2.4.2 property改变模式

/*** This describes how value of property can change.*/
enum VehiclePropertyChangeMode : int32_t {/*** Property of this type must never be changed. Subscription is not supported* for these properties.*/STATIC = 0x00,/*** Properties of this type must report when there is a change.* IVehicle#get call must return the current value.* Set operation for this property is assumed to be asynchronous. When the* property is read (using IVehicle#get) after IVehicle#set, it may still* return old value until underlying H/W backing this property has actually* changed the state. Once state is changed, the property must dispatch* changed value as event.*/ON_CHANGE = 0x01,/*** Properties of this type change continuously and require a fixed rate of* sampling to retrieve the data.  Implementers may choose to send extra* notifications on significant value changes.*/CONTINUOUS = 0x02,
};